Electrodeposition of nickel



United States Patent 3 5 7. ELECTRODEPOSITIQN OF NICKEL V FranlcPassal,Detroit, and Wa'rr'en R. Doty, Claws'on, Mich; a'ssig'riors to M & TGhernicals Inc}, New York, N.., a co 'rpor'ation of Delavva're-No'Dra'vving. Fireman. s1, 1963,8431. No. 255,201- 12 Claims. (Cl'. 204491 Still another object of this invention is to provide supe-- riorbaths for electrodepositing brightand smooth-nickel. The invention alsocontemplates providing a superior method for electrodepositing brightand smooth nickel.

I have discovered that novel substituted pyridine quaternary saltshaving the following general formula are potent primary brighteners innickel electroplating baths.

(C a)d wherein one of the group's'A and B is and the other is a, b, cand d are each 0 or 1; R and R are alkyl groups having 1' to 4 carbonatoms; X and X are anions; and

is selected' from the group consisting of pyridine, quinoline, andisoquinoline.

These compounds may generally be classified as 2,4- di substitutedpyridine compounds, 2,6-disubstituted pyridine compounds,2,4-disubstituted-6 picoline compounds and 2 ,6-disubstituted 4-picolinecompounds.

O f the salts of the type encompassed 'by the general formula, thosethat are in the doubly quaternized form, i.e;, a and b equal 1, arepreferred. These double quaternary nitrogen compounds are prepared byreacting the singly quaternized' compound containing a tertiary nitrogenatom with an' alkylating' agent such as dimethyl sulfate. Thesequaternary compounds may be used per se, or the anionic functional groupmay be replaced by other anions. These anions are from water-solubleacids or water soluble salts. This is illustrated in the replacement ofthe chloride anion by the acetate anions; by

reacting the chloride-containing quaternary with silver acetate. Amongthe common anions useful in the invention are bromide, chloride, iodide,sulfate, methosulfate, ethosulfat'e, chloroacetate, citrate, andperchol'orat'e. The iodides, bromides, methosulfate's andethosulfatesare preferred because of their solubility and compatibility in thestandard nickel plating baths. In the acid nickel plating baths, thesequaternized salts are ionized with the active brightening agent beingthe cation. The active ionized cation which may be present in theplating bath may generally have the formula wherein one of the groups Fand G is and the other is The cation is, obviously, at equilibrium withthe various anions in the'baths.

The quaternary salts of this invention are prepared by reacting'2',6-1utidine;. 2,4-lutidine;' or 2,4,6-collidine' with the pyridine(or the quinoline or the isoquinoline) in a molar ratio of at least 2moles ofthe pyridines per mole of lutidineor collidine in the presence"of iodine- The purified product has the general formula at... twang...

wherein one of the groups D and E is and the other is This is preferablyquaternized" with an alkylating agent such as dimethyl' sulfate byheating together andthen adding water and boiling to volatilize andhydrolyze the excess of alkyla'ting agent.

Illustrative of the preparation of the substituted pyridine quaternarysalts are the following examples:

Example 1 At room temperature 10.7 g. of 2,6-lutidine (0.1 mole)- and 40g. of pyridine were mixed and heated to 115 C. under reflux withstirring. 50.8 g. of iodine (0.2 mole) in ml. of dimethyl formamide wereadded dropwise over a period of 2 hours, during which the temperatureincreased to 139 C. This temperature was then maintained for another 4hours, after which the reaction mix Example 2 The anions present in thesolution, methosulfate, and sulfate, are compatible with the otherconstituents of nickel plating baths. During the quaternization with thealkyla-ting agent the iodide anion is lost by volatilization ashydriodic acid (H1). The reaction product is noted as compound B inTable III.

Example 3 The following were reacted generally according to theprocedure of Example 1: 2.7 grams (0.25 mole) of 2,6- lutidine, 12.7grams (0.05 mole) of iodine, and 30 ml. (0.23 mole) of quinoline wereheated to 130-140 C. for 3 hours, then cooled in ice and filtered. Thecrystals were washed with acetone and recrystallized from ethyl alcoholand water (80% ethanol by volume). The yield was about 10% of a,u'bis(quinolinium iodide) 2,6- lutidine, which is noted as compound C inTable III. Melting point greater than 300 C.dark yellow crystals.

Example 4 1.2 g. of the product of Example 3 was slowly heated with 10ml. of methyl chloracetate. Bubbling began well below 130 C. with thered-colored solid becoming gummy. It was cooled and 10 ml. of ethylalcohol added, boiled for 10 minutes and then cooled in ice. A red oilseparated out. The solvents were removed by vacuum leaving a residue ofred needles. 20 ml. of ethyl alcohol were added and the crystalsfiltered to recover 1 gram. After recrystallization from boiling ethylalcohol and treatment of the hot solution with activated carbon, theyield was about 0.22 g. of light red needles. Melting point 186-190" C.with partial melting at 128 C. The product is noted as compound D inTable III.

Example 5 12.1 g. (0.1 mole) of 2,4,6-collidine was heated to 117 C. ina reaction vessel fitted with a stirrer, reflux condenser and droppingfunnel. 50.8 g. iodine (0.2 mole) dissolved in 100 ml. of pyridine Wasadded dropwise over a one-half hour period to the hot collidine;followed by heating for an additional one and one-half hour at 117 C.The reaction mix was cooled to 6 C. and filtered and washed with acetone(50 ml.). Recovery was 34 g. An additional 23.5 g. was recovered fromthe filtrate after adding more acetone. The product is noted as compoundE in Table III.

Example 6 10 g. of the product of Example 5 plus ml. dimethyl sulfatewas heated slowly to 100 C. and held at this temperature for one hour.It was cooled and 75 ml. of water was added and then boiled until allthe dimethyl sulfate decomposed, followed by treatment with 2 g. ac-

tivated carbon, and filtered. The product is noted as compound F inTable III.

Example 7 10.7 g. (0.1 mole) of 2,4-lutidine was placed in a 500 ml.flask fitted with a stirrer, reflux condenser and dropping funnel. 50.4g. (0.2 mole) of iodine was dissolved in ml. of pyridine and thissolution was added dropwise over a period of one hour while stirring andheating the contents of the flask. The temperature was maintained at 119C. for an additional 2 hours. The mixture was cooled to room temperatureand a mass of light brown crystals precipitated. These were filtered,washed with acetone and air dried to give 70 g. of product. Afterrecrystallization, the product was pale reddish brown in color andmelted sharply at 167-168 C. Iodine analysis by silver nitrate titrationshowed 49.1% iodine (theory 49.3%).

Conventional baths and propesses for electroplating bright nickel aredescribed in Principles of Eleetroplat ing and Electroforming, Blum andHogabootn, ages 362-381, revised third edition, 1949, McGraW-Hill BookCo., Inc., New York; and in Modern Electroplating," edited by A. G.Gray, The Electrochemical Society, 1953, pages 299-355. The control andoperating conditions, including the concentration of the bathingredients, pH, temperature, current density, etc., of theseconventional baths are generally applicable to the present invention.Almost all baths for electroplating bright nickel contain nickel sufate,a choride, usually nickel chloride; a buffering agent, usually boricacid; and a wetting agent, e.g., sodium lauryl sulfate, sodium laurylether sulfate, or 7 ethyl 2 methyl 4 undecanol sulfate. Such bathsinclude the Well-known Watts bath and the high chloride bath. Otherbaths may contain as a source of the nickel a combination of nickelfluoborate with nickel sulfate and nickel chloride, or a combination ofnickel fluoborate with nickel chloride. Typical Watts-type baths andhigh chloride baths are noted in Tables I and II.

TABLE I.WATTS-TYPE BA'IHS Nickel sulfate, g./l. 200 to 400 Nickelchloride, g./l. 30 to 75 Boric acid, g./l. 30 to 50 Temperature, C. 30to 65 pH (electrometric) 2.5 to 4.5

with agitation.

TABLE II.HIGH CHLORIDE BA'IHS Nickel chloride, g./l. to 300 Nickelsulfate, g./l. 40 to 150 Borice acid, g./1. 30 to 50 Temperature, C. 30to 65 pH (electrometric) 2.5 to 4.5

with agitation.

Addition agents as brighteners in bright nickel plating baths aredivided into two classes on the basis of their function. Secondarybrighteners (1) increase the brightness of an ordinarily dull or mattedeposit but not to a full or mirror bright stage and (2) impart aductilizing effect. The use of primary brighteners in conjunc tion withsecondary brighteners results in mirro-bright deposits.

The pyridine quaternary salts of the present invention are potent andextremely effective primary brighteners. The following specific saltsare preferred, as are the baths containing the cationic residue of thesalts:

TABLE III A. a,a'-bis(pyridinium iodide)-2,6-lutidine B. oc,ct'-bl$(pyridinium)-1-methyl-2,6-lutidinium tri:

methosulfate C. a,c:'-bis(quinolinium iodide)-2,6-lutidine TABLEIII-Continued D. mod-bis (quinolinium-1-methylcarboxymethyl) -2,6-

lutidinium" trichloride' E. bis(.pyridi11ium'iodide)-2,4,6 collidine F.bis (pyridinium).-l-methyl-2,4,6-collidine trimetho sulfate G. a,ot'-biS(picolinium iodide) -2,6-lutidine H. a,a-bis(pyridiniumchloride)-2,6-lutidine I. cad-bis (pyridinium)-1-ethyl-2,6-lutidiniumtriethosulfate I. a,oc'-biS (4-ethylquinol-inium iodide) -2,6-lutidineK. na -bis (pyridinium iodide) -2,4-lutidine L. un-bis(pyridinium)-1rnethyl-2,4-lutidinium trimethosulfate M.a,'y-bis(quinoliniurn iodide)-2 ,4-lutidine N.a,'y-bis(pyn'dinium)-1-(methylcarboxymethyl )-2,4-

lutidinium trichloride 0. cc,'y-biS(piCO1inillm iodid'e)-2,4-lutidine P.a,' -bis(pyridinium chloride)-2,4-lu-tidine Q.a,y-bis(pyridinium)-1-ethyl-2,4-lutidinium-trietho sulfate R. a',--bis(4-ethylquinolinium' iodide)-2,4-lutidine These pyridine quaternarysalts are generally used in concentrations between 0101 g./l. and 0.1g./ l., the particular preferred concentrations depend on the secondarybrightener used, its concentration, and such other factors as the degreeof luster, rate of brightening and leveling desired, and the finish ofthe basis metal.

Secondary brighteners which are useful in combinationwith the primarybrighteners, generally in amounts between 1 g./l. up to 75 g./l., andpreferably 1 g./l. to 20 g./l., include such substituted aromaticcompounds as 1,3,6-naphthalene trisulfon'ate, sodium or potassium saltsof saccharin, the sodium or potassium salts of orthosulfobenzaldehyde,the water soluble aryl sulfonic acid and sulfinic acid' compounds, etc.For use in high chloride type nickel plating baths, a preferredsecondary brightener is a sodium or potassium salt of sulfonateddibenzothiophene dioxide, prepared by sulfonating diphenyl with fumingsulfuric acid and isolating and neutralizing the reaction product. Thepreferred secondary brighteners for use with the primary brighteners ofthe present invention are the sodium and potassium salts of saccharin,sulfonated dibenzothiophene dioxide, and sodium 1,3,6-naphthalenetrisulfonate. The secondary brighteners are generally characterized byhaving at least one sulfone or sulfonic acid group attached to a nuclearcarbon. In addition to the usual brightener system of a primarybrightener and a secondary brightener, the system may also contain anauxiliary secondary brightene'r such as: 2-butene- 1,4-diol; orN-vinyl-2-pyrrolidone; or sodium 2-propene-1-sulfonate; or sodium3-chloro-2- butene sulfonate; or the mixed isomers of sodium3-butene-Z-hydroxy-l-sulfonate and sodium3-butcne-l-hydroxy-Z-sulfonate; or sodium 2-propyne-1-sulfonate; orsodium 1-pheny1ethene 2-sulfonate.

For the purpose of giving those skilled in the art a betterunderstanding of the invention, illustrative examples are given. In eachof the examples, an aqueous'acidic nickel-containing bath was made upwith the specified components. Electrodeposition of nickel was carriedout by passing electric current through an electric circuit comprisingan anode and sheet metal or rod cathode, both immersed in the bath; Thebaths were agitated, usually by a moving cathode. Bright electrodepositswere obtained in all the tests included herein as'ex'amples'.

In Examples 1 through 16, the following standard bath was used as a basesolution:

G./l. Nickel sulfate 300 Nickel chloride 60 Boric acid 45 Sodium laurylsulfate 0.5

Anita g./l. C.

Saeeharin (as K salt) Primary Brightener A. Saccharin (as K salt)-Primary Brightener B; Saccharin (as K sa1t) Primary Brightener O 05Saccharin (as K salt) Primary Brightener D acha 'raaK o PrimaryBrightener E I Saceharin (as K sa1t) Primary Brightener F 4 4. 0 0 4 0 40 4 0 4 0 4 0. Saccharin (as K salt)' 4 0 4 0 4 Primary Brightener MSaccharin (as K salt). Primary Brightener B Sulfonated dibenzothiophenedioxide. Primary Brightener Q Suifonated dibenzothio= phene dioxide. 4.0 Saccharin (as K sa1t) Primary Brightener A Sa'ccharin (K salt);

2-butene-1,4-dio1 2 Primary Brightener 0 Saccharin (as K salt) Coumarin0.2 Primary Brightener B 0. 0 Saecharin (as K salt)" 4Phenylpropiolarnide 0 Primary Brightener B 0 0-Su1t0benzaldehyde 3 (Nasalt). Primary Brightener B 0. 1' o sulfobenzaldehyide 3 In Examples 17to 21 inclusive, the following standard bath was used as a basesolution:

G./l. Nickel chloride 250 Nickel sulfate 45 Boric acid 45: Sodium laurylsulfate 0.5

TABLE V Example Additives Amt AJsq. dm. -pH Temp, N0. g./l. C. D. 0.

171 Saccliarin'(asK salt) 4- 40' 4. 0 54 ;Primary Brighte'ner A. 0502'18 .Saceharin (as K salt)- '4 4. 0 4; 0 60 Primary Brightener B '0. 06 I19; Saccharin (asK salt)- ,4 4.0 ;4.0 60

. Primary Brightener M 0. 02 20 Sullonated dibe'nzothio- 4 p'henedioxide. v 4. 0 3. 5 57 Primary Brightener A. 0. 02 21 Sulfonateddibenzothio- 4 phene dioxide. 4. 0 3. 5 57 Primary Brightener B 0. 02

The foregoing examples illustrate specific baths and processes,several'being preferred. It is understood that the compositions andconditions may be varied. Although the potassium' saltswerernost oftenused andarepreferred, they may be partially or completely replaced bysuch other salts as the sodium salts, etc.

The nickel electrodeposits obtained from baths utilizing the novelbrightener combination are advantageous in that mirror-bright lustrouselectrodeposits having ahigh degree of ductility are obtained over awide range of current densities. The bright nickel electrodeposits arepreferably plated on a copper or copper alloy basis metal. However, theymay be electrodeposited directly. on such metals as iron, steel, etc.

As many embodiments of this invention may be made without departing fromthe spirit and scope thereof, it is to be understood that the inventionincludes all such modifications and variations as come within the scopeof theappended claims.

We claim:

1. A process for electroplating mirror-bright nickel comprisingelectrodepositing nickel from an aqueous acid nickel electroplating bathcontaining a secondary brightener and a small effective amount of aprimary brightener to cause the electrodeposition of mirror-brightnickel, said primary brightener being a cation having the structure ah mRo N+OH CH +N R L1 E r J wherein one of the groups and E is and theother is n H N N G H wherein c and d are each to 1; R is an alkyl grouphaving 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline andisoquinoline.

3. A process for electroplating mirror-bright nickel comprisingelectrodepositing nickel from an aqueous acid nickel electroplating bathcontaining a secondary brightener and a small effective amount of aprimary brightener to cause the electrodeposition of mirror-brightnickel, said primary brightener being a cation having the structurewherein one of the groups F and G is and the other is o l H a, c and dare each 0 to 1; R and R are each alkyls of 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline, andisoquinoline.

8 4. A process for electroplating mirror-bright nickel comprisingelectrodepositing nickel from an aqueous acid nickel electroplating bathcontaining a secondary brightener and a small efiective amount of aprimary brightener to cause the electrodeposition. of mirror-brightnickel, said primary brightener being a cation having the structurewherein a, c and d are each 0 to l; R and R are each selected from theclass consisting of alkyl groups having 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline, andisoquinoline.

5. A process for electroplating mirror-bright nickel comprisingelectrodepositing nickel from an aqueous acid nickel electroplating bathcontaining between 1 g./l. and 75 g./1. of a secondary brightenercharacterized by having at least one group selected from sulfone andsulfonic acid groups attached to a nuclear carbon of a homocyclicaromatic ring and between 0.01 g.l. and 0.1 g.l. of a primarybrightener, said primary brightener being a cation having the structureD RQCN+ CH \E)\CH3+NQ R wherein one of the groups D and E is and theother is c and d are each 0 to 1; R is an alkyl of 1 to 4 carbon atoms;and

is selected fromthe group consisting of pyridine, quinoline andisoquinoline.

' 6. A process for electroplating mirror-bright nickel comprisingelectrodepositing nickel from an aqueous acid nickel electroplating bathcontaining between 1 g./l. and 75 g./l. of a secondary brightenercharacterized by having at least one group selected from sulfone andsulfonic acid groups attached to a nuclear carbon of a homocyclicaromatic ring and between 0.01 g./l. and 0.1 g./l. of a primarybrightener, said primary brightener being a cation having the structureR, @q. H.O lCH. R. wherein one of the groups P and G is and the other isa, c and d are each to I; and'R 'a-re each alkyls of 1 to 4 carbonatoms; and

is selectedfromthe-group consisting of pyridine, quinoline andisoquinoline.

1'. An aqueous acid electrolytic bath containing soluble nickel saltsfor the electrod'epositions of mirror-bright nickel, containing. asecondary brightener and between 0.01 g./1. and 0.1 g./l. of a primarybrightener, said primary brightener being? a-. cation having, thestructure wherein one of the groups D and E is and the other is c and dare each 0 to 1; R is an alkyl of 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline andisoquinoline.

8. An aqueous acid electrolytic bath containing soluble nickel salts forthe electrodeposition of mirror-bright nickel, containing a secondarybrightener and between 0.01 g./l. and 0.1 g./l. of a primary brightener,said primary brightener being a cation having the' structure wherein cand dare each 0 to 1; R is an alkyl group having 1 to 4 carbon atoms;and

is selected from the group consisting of pyridine, quinoline andisoquinoline.

9. An aqueous acid electrolytic bath containing soluble nickel salts forthe electrodeposition of mirror-bright nickel, containing a secondarybrightener and between 0.01 g./l. and 0.1 g./l. of a primary brightener,said primary brightener being a cation having the structure I aLiwherein one of the groups P and G is and the other is 10: a, c and d areeach 0 to 1; R and R are e'ach alky-ls of 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline, andisoquinoline.

10. An aqueous acid electrolytic bath containing soluble nickel saltsfor the electrodeposition of mirror-bright nickeL, containing a.secondary brightener and: between 0101. g ./'l and g./'l., ofa. primarybrightener, said primary brightener beingv a cation having, thestructure (encam c N+H (3- L/ u R.

wherein a, c and d are each 0 to 1; R and R' are each selected from theclass consisting of alkyl groups having 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline, andisoquinoline.

11. An aqueous acid electrolytic bath containing soluble nickel saltsfor the electrodeposition of mirror-bright nickel, containing between0.01 g./l. and 0.1 g./l. of a primary brightener, said primarybrightener being a cation having the structure c and d are each 0 to 1;R is an alkyl of 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quinoline andisoquinoline; and between 1 g./l. and 20 g./l. of a secondary brightenerselected from the class consisting of the sodium and potassium salts ofsaccharin, sulfonated dibenzothiophene dioxide, and 1,3,6-naphthalenetrisulfonate.

12. An aqueous acid electrolytic bath containing soluble nickel saltsfor the electrodeposition of mirror-bright nickel, containing between0.01 g./l. and 0.1 g./l. of a primary brightener, said primarybrightener being a cation having the structure wherein one of the groupsF and G is and the other is a, c and d are each 0 to 1; R and R are eachalkyls of 1 to 4 carbon atoms; and

is selected from the group consisting of pyridine, quino- 10 ReferencesCited by the Examiner UNITED STATES PATENTS Shenk 204-49 Harris 26 0290DuRose et a1. 204-49 Luvisi 260290 Vellani 260290 Towle 2 O449 Passal204-49 JOHN H. MACK, Primary Examiner.

MURRAY TILLMAN, Examiner.

15 A. B. CURTIS, G. KAPLAN, Assistant Examiners.

1. A PROCESS FOR ELECTROPLATING MIRROR-BRIGHT NICKEL COMPRISING ELECTRODEPOSITING NICKEL FROM AN AQUEOUS ACID NICKEL ELECTROPLATING BATH CONTAINING A SECONDARY BRIGHTENER AND A SMALL EFFECTIVE AMOUNT OF A PRIMARY BRIGHTENER TO CAUSE THE ELECTRODEPOSITION OF MIRROR-BRIGHT NICKEL, SAID PRIMARY BRIGHTENER BEING A CATION HAVING THE STRUCTURE 